Floating Wind Turbine Pitch Damping Against Negative Aerodynamic Coupling
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Solution Overview
Problem
Floating wind turbines experience negative damping effects due to dynamic coupling between motion and aerodynamic torque, leading to generator speed oscillations and platform instability, particularly when the wind turbine moves into or out of the wind.
Innovation Solution
A method and system for damping wind turbine motion by generating damping signals based on motion and wind direction signals, adjusting phase and amplitude of these signals using gain scheduling parameters, and controlling blade pitch angles to stabilize the turbine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the pitch controller collectively pitches the blades to reduce generator speed, then the generator speed is controlled, but the thrust is reduced which causes the wind turbine to move forwards more amplifying the effect (negative damping)
Solution Approach 1:
The patent implements a feedback control mechanism where the motion of the floating platform is sensed and used to modulate the collective pitch reference. The feedback signal is derived from the platform's acceleration or velocity and is used to counteract the motion-induced changes in aerodynamic torque. This closed-loop feedback approach compensates for the negative damping effect by adjusting the pitch reference in response to actual platform motion, thereby stabilizing both generator speed and platform position simultaneously.
Solution Approach 2:
The patent applies preliminary action by modifying the collective pitch reference in advance based on predicted or measured platform motion. Rather than waiting for generator speed deviations to occur, the system proactively adjusts the pitch reference to counteract the expected aerodynamic torque changes caused by platform motion. This preemptive adjustment prevents the oscillatory behavior before it develops, maintaining both speed control and platform stability.
2Power
If the wind turbine moves into the wind increasing aerodynamic torque and generator speed, then the generator speed increases, but this creates a coupling effect that promotes further motion
Solution Approach 1:
The feedback mechanism senses platform motion and generates a compensatory signal that modulates the collective pitch reference. When the platform moves into the wind, the feedback signal adjusts the pitch reference to reduce aerodynamic torque, counteracting the motion-induced power increase. This feedback loop breaks the positive feedback cycle between platform motion and aerodynamic torque, preventing oscillatory instability while allowing normal power generation.
Solution Approach 2:
The system applies preliminary anti-action by introducing a counteracting pitch reference modulation that opposes the motion-induced aerodynamic torque changes. When platform motion tends to increase aerodynamic torque, the control system preemptively adjusts the pitch reference to reduce thrust, creating an opposing force that counteracts the motion. This anti-action prevents the coupling effect from developing into sustained oscillations.
Data Source
AI summary
A method of damping motion of a wind turbine, the wind turbine comprising a rotor and a floating platform. A motion signal is generated which is indicative of a motion of the wind turbine. A wind direction signal is generated which is indicative of a wind direction relative to the floating platform. A damping signal is generated on the basis of the motion signal and the wind direction signal, and the motion of the wind turbine is damped on the basis of the damping signal, for instance by adjusting the pitch of the rotor blades. A phase of the damping signal may be controlled on the basis of the wind direction signal.